I did not write OpenRocket, but I currently contribute to
it. OpenRocket is a free, open source, fully featured model rocket
simulator that allows you to design and simulate your rockets
before actually building and flying them.

This tool allows one to load an OpenRocket model &
simulation, specify a number of variable parameters, and run a
large number of simulations, monte-carlo style, to generate an
expected landing area and understand variations in maximum
altitude.

Variable paramters are likely to include:

Construction variations in weight, fin angle & finish
smoothness.

Atmospheric conditions.

Launch parameters.

Exceptional events (CATO, chute failure, ignition
failure).

The flight path visualization may also end up being
contributed into the core OpenRocket GUI if there is interest.